This invention relates generally to the field of connection devices for electrical cables and the like. In particular, it relates to a self-locking, strain-relief end bell for use in such connection devices.
Typically, an electrical cable connection assembly comprises a male connector, a female connector, a coupling ring or nut that couples the male and female connectors, and a strain-relief member or "end bell" for each of the connectors.
There are several important considerations in designing connector assemblies. First, the connectors must be capable of being quickly and easily coupled and decoupled without special tools, and with the use of no more than moderate manual effort. Second, the connectors, once coupled, must maintain good electrical contact with each other. In the aerospace field, this second consideration dictates that such connector assemblies must be able to withstand severe vibrational forces without uncoupling. To this end, the connector industry has devised a number of connector assembly designs in which the coupling ring or nut has a self-locking, or anti-decoupling, mechanism for the purpose of resisting vibration-induced decoupling. These self-locking mechanisms typically employ ratcheting means between the coupling nut and one of the connectors for allowing the coupling nut to move more easily in the coupling or tightening direction than in the decoupling or loosening direction.
The following United States patents exemplify the approaches taken by the prior art in this area: U.S. Pat. Nos. 3,552,777-Heinrich et al.; 3,678,439- Vetter; 3,750,087- Vetter; 3,869,186- Vetter; 4,030,789- Paoli; 4,255,008- Snyder et al.; 4,407,529- Holman; 4,508,407- Ball; 4,588,246-Schildkraut et al.; and 4,588,245- Schwartz et al.
While prior art anti-decoupling mechanisms for success, several shortcomings have been noted. For example, some prior art devices may require excessive manual effort for decoupling. Others may exhibit a tendency to fail after a number of coupling/decoupling operations. Several achieve satisfactory results, but only with relatively complex mechanisms that are costly to manufacture.
Moreover, the prior art has focused on the coupling between the two connectors. By and large, the interface between each connector and its associated strain-relief end bell has been ignored. To date, therefore, there has been no satisfactory way devised to minimize vibration-induced decoupling between the end bell and the connector. The typical end bell comprises a cable clamp that attaches to the connector by an internally-threaded coupling ring. This arrangement is prone to vibration-induced decoupling. To prevent such decoupling, some mechanics have developed the practice of securing the end bell to the connector with a length of wire. A serious problem with this practice, however, is that a piece of the wire occasionally works loose or falls off, with the possibility of causing a short circuit if it lodges in contact with other electrical components.
Accordingly, there has been a long-felt, but as yet unmet need for a strain-relief end bell that has a simple, yet reliable, anti-decoupling feature. Moreover, there is a need for such a self-locking end bell that is not appreciably larger or heavier than conventional end bells, especially in the aerospace industry, where minimizing weight is always a vital concern. Furthermore, an end bell with these features should also be relatively simple and economical to manufacture.